If you have winter squash and are wanting to preserve it remember that you can NOT home can pumpkin or winter squash puree. If you want it pureed then you should freeze it. If you want to can it, it must done in a pressure canner and only when cut into 1 inch cubes.
According to the Elizabeth L. Andress, Ph.D., Associate Professor and Extension Food Safety Specialist, Department of Foods and Nutrition, home canning is not recommended for pumpkin butter or any mashed or pureed pumpkin or winter squash. In 1989, the USDA’s Extension Service published the Complete Guide to Home Canning that remains the basis of Extension recommendations today, found in the September 1994 revision. The only directions for canning pumpkin and winter squash are for cubed pulp. In fact, the directions for preparing the product include the statement, “Caution: Do not mash or puree.”
Some of the factors that are critical to the safety of canned pumpkin products are the viscosity (thickness), the acidity and the water activity. Pumpkin and winter squash are also low-acid foods (pH > 4.6) capable of supporting the growth of Clostridium botulinum bacteria which can cause the very serious illness, botulism, under the right storage conditions. If the bacteria are present and survive processing, and the product has a high enough water activity, they can thrive and produce toxin in the product.
To process using a hot pack, wash pumpkin or squash and remove the seeds. Cut into 1 inch slices and peel. Cut the flesh into 1 inch cubes. Add to a saucepot of boiling water, boil 2 minutes. Pack the hot cubes into hot jars, leaving 1 inch headspace. Fill jar to 1 inch from top with boiling hot cooking liquid. Remove the air bubbles. Wipe jar rims, adjust lids and process.
Table 1. Recommended process time for Pumpkin and Winter Squash in a dial-gauge pressure canner. | ||||||
Canner Pressure (PSI) at Altitudes of | ||||||
Style of Pack | Jar Size | Process Time | 0 – 2,000 ft | 2,001 – 4,000 ft | 4,001 – 6,000 ft | 6,001 – 8,000 ft |
Hot | Pints | 55 min | 11 lb | 12 lb | 13 lb | 14 lb |
Quarts | 90 | 11 | 12 | 13 | 14 |
Table 2. Recommended process time for Pumpkin and Winter Squash in a weighted-gauge pressure canner. | ||||
Canner Pressure (PSI) at Altitudes of | ||||
Style of Pack | Jar Size | Process Time | 0 – 1,000 ft | Above 1,000 ft |
Hot | Pints | 55 min | 10 lb | 15 lb |
Quarts | 90 | 10 | 15 |